Doesn't coinpayments lock the rate for like 6 hours? 15 minutes sounds very short especially if the transaction has to confirm within that timespan.
Now I'm even more confused. If 15 mins is short, then why they even mark this as something worth noticing on their site?
And, if 15 mins is a lot - then where the 6 hours came from? What's the deal with this time difference in hours?..
The user who talked about 6 hours doesn't know what he is talking about. He is probably talking about something else.
We are talking about market prices, which change every second. There is no sense in making a fixed value for hours.
They just mark 15 minutes on their sites for operational reasons, problably. You won't be making money in those 15 minutes. If there is big price change, they will refund you and won't make the exchange. They are not going to pay a price very different from with anything happen in those 15minutes.